Top row: Natural stimuli. Bottom row: Artificial stimuli. (A) Conditional probability of estimated tilts given groundtruth tilt in the unsigned tilt domain: [0, 180°). Each column of each subplot represents the conditional probability distribution of estimates for a different groundtruth tilt. Hence, each column represents the data in each subplot of Figure 3. (B) Conditional probability of groundtruth tilts given estimated tilt. Each row of each subplot represents the conditional probability distribution of groundtruth tilts for a different estimate. Hence, each row represents the data in each subplot of Figure 4. (C,D) Same as (A,B) but in the signed tilt domain: [0°, 360°). For visualization, each conditional probability distribution is normalized so that the maximum probability equals 1.0 (colorbar). The distributions of tilt estimates from natural and artificial stimuli conditional on groundtruth tilts are very different (A,C). By contrast, the distributions of groundtruth tilts conditional on estimates from natural and artificial stimuli are very similar (B,D). Thus, regardless of the stimulus type, the information provided about groundtruth by human tilt estimates is of similar quality. This property of the estimates should simplify subsequent processing that combines local into more global estimates (see main text).